LED light emitting devices employing LEDs have been widely used as light sources for various illumination and display devices. Further, an LED light emitting device has also been developed and used, wherein plural types of LEDs that emit different colors from semiconductor light emitting elements such as LED chips, are used in combination so that the respective emission colors are combined to obtain a desired radiation color. For example, Patent Document 1 discloses an LED light emitting device wherein three types of LEDs that emit e.g. blue light, green light and red light, are used in combination, and drive currents to be supplied to the respective LEDs are adjusted, so that the lights emitted from the respective LEDs are combined to obtain a desired white light.
In nature, a semiconductor light emitting element itself has a relatively narrow emission spectrum width, and if light emitted from such a semiconductor light emitting element itself is used for illumination as it is, there may be a problem that color rendering properties which become important in usual illumination, tend to be low. Therefore, in order to solve such a problem, LED has been developed wherein light emitted from a semiconductor light emitting element is subjected to wavelength conversion by means of a wavelength conversion member such as a phosphor, followed by emission, and an LED light emitting device wherein such LEDs are used in combination, is disclosed in e.g. Patent Document 2. In the LED light emitting device in Patent Document 2, blue LED employing a semiconductor light emitting element to emit blue light, green LED having combined to the blue light emitting element a green phosphor to be excited by the blue light emitted from the blue light emitting element, to emit green light, and red LED having combined to the blue light emitting element a red phosphor to be excited by the blue light emitted from the blue light emitting element, to emit red light, are used. And, by combining lights emitted respectively from these blue, green and red LEDs, it is possible to secure excellent color rendering properties, and by adjusting the light outputs of the respective LEDs, it is possible to variously change the radiation color of the LED light emitting device.
Thus, it is possible to variously change the radiation color of the LED light emitting device by using plural types of LEDs that are different in emission color, and accordingly, various proposals have been made to apply the LED light emitting device to an indicator to carry out an indication by the change of the radiation color. For example, Patent Document 3 proposes a combination meter for a vehicle, in which the LED light emitting device is applied for illumination. That is, in the combination meter in Patent Document 3, white LED to emit white light and orange LED to emit orange light are used for transmissive illumination of a dial face, and it is so designed that the position of illumination by orange light is changed in accordance with the movement of an indicating needle, by illuminating a site of the dial face corresponding to the position of the indicating needle, with orange light and at the same time, illuminating other sites of the dial face with white light.
Further, Patent Document 4 proposes a meter device for a vehicle, wherein an LED light emitting device comprising red LED to emit red light and green LED to emit green light, is used for illumination. The meter device in Patent Document 4 is designed so that illumination is carried out by green light until the travelling speed of the vehicle, the engine rotation speed or the like exceeds the upper limit value, and when it has exceeded the upper limit value, the illumination is switched to illumination by red light. Further, Patent Document 4 proposes to combine yellow LED to emit yellow light, in addition to the red and green LEDs.
These Patent Documents 3 and 4 are to increase the visibility of an indicator by switching between emissions of light from two types of LEDs having different emission colors. Patent Document 5 proposes a digital speed meter device for a vehicle, which is designed to variously change the indication color by combining emission colors by means of plural types of LEDs having different emission colors. In the meter device in Patent Document 5, an LED device is used which comprises red LED to emit red light, green LED to emit green light and blue LED to emit blue light, and it is designed to change the illumination color in the order of white, green, blue, yellow, orange and red as the traveling speed of the vehicle increases, by using lights emitted from these LEDs alone or in combination. Further, in Patent Document 5, it is also proposed to provide an auxiliary indication region to be used in combination with such a meter device, and it is designed to change the illumination color of the auxiliary indication region in the order of green, yellow and red as the travelling speed of the vehicle increases, by means of an LED light emitting device comprising red LED and green LED.